I plan to study the structure of ribosomal RNA, and the role of certain of its structural features in ribosome function, and in interaction with other RNA such as transfer and messenger RNA. Emphasis will be placed on (1) the mitochondrial protein-synthesizing system of cultured hamster cells, and comparison with homologous constituents of insect and yeast mitochondria; (2) the rRNA of several bacterial species that may be related biochemically or evolutionarily to mitochondria (mycoplasma, Paracoccus denitrificans, Rhodopseudomonas spheroides); (3) that of staphylococcus aureus, to further elucidate earlier findings on the role of rRNA methylation in acquired resistance to erythromycin; (4) re-examination of the modification status of the rRNA and ribosomal precursor RNA of E. coli: and (5) the 5'-terminal sequences of various mRNA's specified by togaviruses, including the alphavirus Sindbis and the flaviviruses Dengue. We shall employ mammalian, insect, fungal and bacterial cell culture systems. Our analytical approaches will include in vivo labeling of cells using (methyl-3H)methionine and 32Pi; in vitro end-labeling of RNA using 32P- ATP and pCp; analysis of methylated nucleotide composition using enzymatic and chemical degradation followed by electrophoretic and chromatographic separations; and sequence analysis using oligonucleotide fingerprinting and "ladder" procedures.